Wireless communication apparatus and channel allocation method

ABSTRACT

Disclosed is a base station in which the frequency usage efficiency can be improved when the communication bandwidths are asymmetric in the uplink line and the downlink line. A base station can communicate by using a plurality of downlink unit bands and a smaller number of uplink unit bands. A control unit allocates uplink resource allocation information and downlink resource allocation information to a PDCCH which is arranged in each of the plurality of downlink unit bands, and allocates a response signal to the uplink line data to a PHICH which is arranged in the same number of downlink unit bands from the plurality of downlink unit bands as there are uplink unit bands. A transmit RF unit transmits the resource allocation information or the response signal.

BACKGROUND Technical Field

The present invention relates to a radio communication base stationapparatus, radio communication terminal apparatus and channel assignmentmethod.

Description of the Related Art

In 3GPP-LTE, an OFDMA (Orthogonal Frequency Division Multiple Access) isadopted as a downlink communication scheme. In a radio communicationscheme adopting 3GPP LTE, a radio communication base station apparatus(hereinafter simply “base station”) transmits a synchronization channel(“SCH”) and broadcast channel (“BCH”) using predetermined communicationresources. Then, first, a radio communication terminal apparatus(hereinafter simply “terminal”) secures synchronization with the basestation by capturing the SCH. After that, the terminal obtainsparameters unique to the base station (such as a frequency bandwidth) byreading BCH information (see Non-Patent Literatures 1, 2 and 3).

Also, in 3GPP LTE, HARQ (Hybrid Automatic Repeat reQuest) is applied touplink data transmitted from the terminal to the base station in uplink.In HARQ, the base station performs CRC (Cyclic Redundancy Check)detection of uplink data and feeds back an ACK (Acknowledgement) ifCRC=OK (no error) or a NACK if CRC=NG (error present), to a mobilestation as a response signal. These response signals are transmitted viaa physical channel for downlink response signal transmission such asPHICH (Physical Hybrid-ARQ Indicator Channel).

Also, standardization of 3GPP LTE-advanced, which realizes fastercommunication than 3GPP LTE, has been started (see Non-Patent Literature4). The 3GPP LTE-advanced system (hereinafter “LTE+ system”) follows the3GPP LTE system (hereinafter “LTE system”).

CITATION LIST Non-Patent Literature

-   [NPL 1] 3GPP TS 36.211 V8.3.0, “Physical Channels and Modulation    (Release 8),” May 2008-   [NPL 2] 3GPP TS 36.212 V8.3.0, “Multiplexing and channel coding    (Release 8),” May 2008-   [NPL 3] 3GPP TS 36.213 V8.3.0, “Physical layer procedures (Release    8),” May 2008-   [NPL 4] 3GPP TR 36.913 V8.0.0, “Requirements for Further    Advancements for E-UTRA (LTE-Advanced) (Release 8),” June 2008

SUMMARY Technical Problem

In 3GPP LTE-advanced, to realize downlink transmission speed equal to orgreater than maximum 1 Gbps, it is expected to adopt a base station andterminal that can perform communication in a wideband frequency equal toor greater than 40 MHz. Also, in 3GPP LTE-Advanced, communicationbandwidths may be made asymmetric between uplink and downlink, takinginto account the difference between a throughput request for uplink anda throughput request for downlink. To be more specific, in 3GPPLTE-Advanced, the downlink communication bandwidth may be made widerthan the uplink communication bandwidth.

Here, a base station supporting the LTE+ system (hereinafter “LTE+ basestation”) is designed to be able to perform communication using aplurality of “component bands.” Here, a “component band” is a bandhaving a maximum 20 MHz width, and is defined as a reference unit of acommunication band. Further, a “component band” in downlink (hereinafter“downlink component band”) may be defined as a band divided by downlinkfrequency band information in a BCH broadcasted from a base station or aband defined by bandwidth in a case where a physical downlink controlchannel (PDCCH) is placed in the frequency domain in a distributedmanner. Also, a “component band” in uplink (hereinafter “uplinkcomponent band”) may be defined as a band divided by uplink frequencyband information in a BCH broadcasted from a base station or a referenceunit in a communication band equal to or below 20 MHz including a PUCCHat both end parts. Also, a “component band” may be expressed as“component carrier(s)” in English in 3GPP LTE.

An LTE+ base station supports an LTE+ system support terminal(hereinafter “LTE+ terminal”). LTE+ terminals include a terminal thatcan perform communication using only one component band (hereinafter“type-1 LTE+ terminal”) and a terminal that can perform communicationusing a plurality of component bands (hereinafter “type-2 LTE+terminal”). Also, the LTE+ base station needs to support not only theabove LTE+ terminal but also a terminal that supports the LTE system andthat can perform communication using only one component band(hereinafter “LTE terminal”). That is, the LTE+ system is designed to beable to assign a plurality of component bands to single communication,and follows the LTE system in which single communication isindependently assigned to each component band.

FIG. 1 and FIG. 2 show an example of placing channels in the LTE+ systemin which communication bandwidths (i.e., the numbers of component bands)are asymmetric between uplink and downlink. In FIG. 1 and FIG. 2, in theLTE+ system, the downlink communication bandwidth is 40 MHz includingtwo downlink component bands, and the uplink communication bandwidth is20 MHz including one uplink component band.

In the downlink shown in the upper part of FIG. 1, PHICH's and PDCCH'sare placed over component bands 1 and 2 in a distributed manner. Also,an SCH that can be received by the LTE terminal and LTE+ terminal(hereinafter simply “SCH”) and a BCH that can be received by the LTEterminal and LTE+ terminal (hereinafter simply “BCH”) are placed nearthe center frequencies of downlink component bands 1 and 2. Also, asshown in the lower part of FIG. 1, a physical uplink data channel(“PUSCH”) is placed in the whole uplink component band in a distributedmanner, and a PUCCH is placed in both sides of the PUSCH. Also, downlinkcomponent bands 1 and 2 are associated with one uplink component band.For example, in a case where communication is performed using only onecomponent band, even when either of two mutually-different downlinkcomponent bands 1 and 2 is used as downlink, the same uplink componentband is used as uplink.

Also, an LTE+ base station assigns a response signal for uplink data,which is placed in a PUSCH and then transmitted, to a PHICH, and feedsback the result to a terminal. Here, for example, the PHICH resourcenumber indicating the PHICH resource position is defined in associationwith the PUSCH resource block (“RB”) number. That is, the PHICH resourcenumbers of PHICH's in component bands 1 and 2 shown in FIG. 1 areassociated with respective PUSCH RB numbers.

Also, each terminal receives a response signal assigned to a PHICHplaced in the same downlink component band as that of a PDCCH to whichresource allocation information for that terminal is assigned. Then, theterminal finds the PHICH resource number of the PHICH to which theresponse signal for uplink data is assigned, from the RB number of aPUSCH to which the uplink data is assigned. For example, as shown inFIG. 1, when resource allocation information for the subject terminal isassigned to the PDCCH placed in downlink component band 1, this terminalreceives as response signal assigned to the PHICH placed in downlinkcomponent band 1. On the other hand, as shown in FIG. 1, when resourceallocation information for the subject terminal is assigned to the PDCCHplaced in downlink component band 2, this terminal receives a responsesignal assigned to the PHICH placed in downlink component band 2.

However, in FIG. 1, if one of PHICH's in downlink component band 1 and 2associated with the same PUSCH (the same RB number) is used, the otherPHICH is not used. That is, PHICH's associated with the same PUSCH (thesame RB number) are redundantly placed in downlink component bands 1 and2. Therefore, only a half of resources for PHICH's placed in downlinkcomponent bands 1 and 2 is probabilistically used, and, consequently,the overhead of PHICH resources increases. Therefore, with the PHICH andPDCCH placement shown in FIG. 1, the use efficiency of frequencydegrades.

In contrast, with the downlink shown in FIG. 2, a PHICH and PDCCH areplaced only in one downlink component band.

In FIG. 2, the downlink includes a downlink component band in which anLTE terminal and LTE+ terminal can perform communication (hereinafter“LTE/LTE+ coexisting band”) and a downlink component band in which onlythe LTE+ terminal can perform communication (hereinafter “LTE+ band”).An SCH/BCH is placed in the LTE/LTE+ coexisting band, and both the LTEterminal and the LTE+ terminal can access an LTE+ base station in theLTE/LTE+ coexisting band. In contrast, in the LTE+ band, the SCH/BCHthat can be received by the LTE terminal is not placed, and a physicaldownlink shared channel (“PDSCH”) is placed.

Therefore, the LTE terminal and LTE+ terminal receive resourceallocation information assigned to a PDCCH placed in the LTE/LTE+coexisting band, and receive a response signal assigned to a PHICHplaced in the LTE/LTE+ coexisting band. Here, even in a case of usingthe LTE/LTE+ coexisting band and LTE+ band shown in FIG. 2, the type-2LTE+ terminal that can perform communication using a plurality ofcomponent bands uses the PDCCH and PHICH placed in the LTE/LTE+coexisting band.

According to the placement example shown in FIG. 2, a PHICH is notplaced in the LTE+ band, and, consequently, resources that can be usedas a PDSCH increase compared to FIG. 1.

However, in FIG. 2, although resources for a PDSCH placed in the LTE+band increase, a PDCCH required to allocate a PDSCH to each terminal isplaced only in the LTE/LTE+ coexisting band. Therefore, the amount ofPDCCH resources is not sufficient; PDSCH's cannot be assignedefficiently, and, consequently, there is a high possibility that the useefficiency of PDSCH's degrades. Therefore, even with the PHICH and PDCCHplacement shown in FIG. 2, the use efficiency of frequency degrades.

Thus, if communication bandwidths (the numbers of bands) are madeasymmetric between uplink and downlink, the use efficiency of frequencymay degrade depending on PHICH and PDCCH placement.

Therefore embodiments of the present invention provide a base station,terminal and channel assignment method for improving the use efficiencyof frequency in a case where communication bandwidths are asymmetricbetween uplink and downlink.

Solution to Problem

The base station of the present invention, which is a radiocommunication base station apparatus that can perform communicationusing a plurality of downlink component bands and a smaller number ofuplink component bands than the plurality of downlink component bands,employs a configuration having: a control section that assigns resourceallocation information to a first channel placed in each of theplurality of downlink component bands and assigns a response signal foruplink data to a second channel placed in a same number of partialdownlink component bands as the uplink component bands; and atransmitting section that transmits the resource allocation informationor the response signal.

The terminal of the present invention, which is a radio communicationterminal apparatus that can perform communication using a plurality ofdownlink component bands and a smaller number of uplink component bandsthan the plurality of downlink component bands, employs a configurationhaving: an obtaining section that obtains resource allocationinformation for the radio communication terminal apparatus assigned to afirst channel placed in each of the plurality of downlink componentbands; a mapping section that maps uplink data on the uplink componentbands according to the resource allocation information of uplink data;and an extracting section that extracts a response signal for the uplinkdata from a second channel placed in a same number of partial downlinkcomponent bands as the uplink component bands.

The channel assignment method of the present invention for assigning asecond channel to a response signal for uplink data in the radiocommunication base station apparatus that can perform communicationusing a plurality of downlink component bands and a smaller number ofuplink component bands than the plurality of downlink component bands,includes: assigning resource allocation information to a first channelplaced in each of the plurality of downlink component bands; andassigning a response signal for the uplink data to a second channelplaced in a same number of partial downlink component bands as theuplink component bands, among the plurality of downlink component bands.

Advantageous Effects of Invention

According to the present invention, it is possible to improve the useefficiency of frequency in a case where communication bandwidths areasymmetric between uplink and downlink.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows an example of PHICH and PDCCH placement;

FIG. 2 shows an example of PHICH and PDCCH placement;

FIG. 3 is a block diagram showing a configuration of a terminalaccording to Embodiment 1 of the present invention;

FIG. 4 is a block diagram showing a configuration of a base stationaccording to Embodiment 1 of the present invention;

FIG. 5 shows an example of PHICH and PDCCH placement according toEmbodiment 1 of the present invention;

FIG. 6 shows an example of PHICH and PDCCH placement according toEmbodiment 2 of the present invention;

FIG. 7 is a block diagram showing a configuration of a terminalaccording to Embodiment 3 of the present invention;

FIG. 8 is a block diagram showing a configuration of a base stationaccording to Embodiment 3 of the present invention;

FIG. 9 shows an example of PHICH and PDCCH placement according toEmbodiment 3 of the present invention;

FIG. 10 shows component bands managed by a base station according toEmbodiment 5 of the present invention;

FIG. 11 shows an example of PHICH and PDCCH placement according toEmbodiment 5 of the present invention;

FIG. 12 shows an example of PHICH and PDCCH placement according toEmbodiment 6 of the present invention; and

FIG. 13 shows a variation of the present invention.

DETAILED DESCRIPTION

Taking into account the above problems, the present invention focuses onthe fact that, while an LTE terminal can perform communication only inan LTE/LTE+ coexisting band in which an SCH and BCH are placed, thetype-2 LTE+ terminal can perform communication using both downlinkcomponent bands of the LTE/LTE+ coexisting band and LTE+ band. That isin the LTE/LTE+ coexisting band, all terminals supported in an LTE+system can read information.

Also, the present invention focuses on the fact that a PDCCH and PHICHare placed depending on uplink resources or downlink resources. To bemore specific, uplink resource allocation information indicating uplinkresources (e.g., PUSCH) to assign uplink data of terminals, and downlinkresource allocation information indicating downlink resources (e.g.,PDSCH) to assign downlink data for terminals, are assigned to PDCCH'sand then reported to each terminal. Therefore, a PDCCH needs to beplaced according to the amounts of uplink resources and downlinkresources. In contrast, PHICH's (PHICH resource numbers) and PUSCH's(PUSCH RB numbers) are associated. Therefore, a PHICH needs to be placedaccording to the number of PUSCH RB's. That is, a PHICH needs to beplaced according to only the amount of uplink resources.

Therefore, with the present invention, the LTE+ base station assignsresource allocation information of uplink data and downlink data toPDCCH's placed in respective downlink component bands, and assigns aresponse signal for the uplink data to PHICH's placed in a same numberof partial downlink component bands (LTE/LTE+ coexisting bands) as thenumber of uplink component bands, among the plurality of downlinkcomponent bands. Also, the type-2 LTE+ terminal maps uplink data onuplink component bands according to resource allocation information forthat terminal assigned to PDCCH's placed in respective downlinkcomponent bands, and extracts a response signal for the uplink data fromPHICH's placed in a same number of partial downlink component bands(LTE/LTE+ coexisting bands) as the number of uplink bands among theplurality of downlink component bands.

Now, embodiments of the present invention will be explained in detailwith reference to the accompanying drawings.

Also, in embodiments, the same components will be assigned the samereference numerals and their overlapping explanation will be omitted.

Embodiment 1

FIG. 3 is a block diagram showing a configuration of terminal 100according to the present embodiment. Terminal 100 is a type-2 LTE+terminal that can perform communication using a plurality of downlinkcomponent bands at the same time.

RF receiving section 102 is designed to be able to change a receptionband. RF receiving section 102 performs radio reception processing (suchas down-conversion and analog-to-digital (A/D) conversion) of a radioreception signal (OFDM signal in this case) received in the receptionband via antenna 101, and outputs the resulting reception signal to CP(Cyclic Prefix) removing section 103.

CP removing section 103 removes a CP from the reception signal and FFT(Fast Fourier Transform) section 104 transforms the reception signalwithout a CP into a frequency domain signal. This frequency domainsignal is outputted to frame synchronization section 105.

Frame synchronization section 105 searches for an SCH included in thesignal received as input from FFT section 104 and finds synchronization(frame synchronization) with base station 200 (described later). Also,frame synchronization section 105 finds a cell ID associated with asequence used for the SCH (SCH sequence). That is, frame synchronizationsection 105 performs the same processing as in a normal cell search.Then, frame synchronization section 105 outputs frame synchronizationtiming information indicating the frame synchronization timing and thesignal received as input from FFT section 104, to demultiplexing section106.

Demultiplexing section 106 demultiplexes the signal received as inputfrom frame synchronization section 105 into the BCH, response signal(i.e., PHICH signal), control signal (i.e., PDCCH signal) and datasignal (i.e., PDSCH signal), based on the frame synchronization timinginformation received as input from frame synchronization section 105.Here, upon receiving the PHICH signal, demultiplexing section 106extracts a response signal for uplink data of the subject terminal fromthe demultiplexed PHICH signal, according to a downlink component bandand PHICH resource number indicated by resource control informationreceived as input from resource control section 108. That is,demultiplexing section 106 extracts the response signal for the uplinkdata of the subject terminal from the PHICH placed in LTE/LTE+coexisting bands, which are a same number of partial downlink componentbands as the number of uplink component bands among a plurality ofdownlink component bands and in which an SCH/BCH is placed. Then,demultiplexing section 106 outputs the BCH to broadcast informationreceiving section 107, the PHICH signal to PHICH receiving section 109,the PDCCH signal to PDCCH receiving section 110 and the PDSCH signal toPDSCH receiving section 111.

Broadcast receiving section 107 reads the content of the BCH received asinput from demultiplexing section 106, associates the RB number of thePUSCH with the PHICH resource number of the PHICH and obtains PHICHresource information indicating the number of PHICH resources. Then,broadcast information receiving section 107 outputs the PHICH resourceinformation to resource control section 108.

Resource control section 108 specifies a PHICH to which a responsesignal for uplink data of the subject terminal is assigned, based on thePHICH resource information received as input from broadcast informationreceiving section 107 and uplink resource allocation informationreceived as input from PDCCH receiving section 110. Here, the PHICH isplaced in part of the plurality of downlink component bands. Therefore,resource control section 108 specifies a downlink component band inwhich the PHICH is placed, based on the PHICH resource information.Further, based on the uplink resource allocation information, resourcecontrol section 108 specifies the PHICH resource number of the PHICHassociated with the RB number of a PUSCH used to transmit the uplinkdata of the subject terminal. Then, resource control section 108 outputsresource control information, which indicates the specified downlinkcomponent band and the PHICH resource number of the PHICH, todemultiplexing section 106.

PHICH receiving section 109 decodes the PHICH signal received as inputfrom demultiplexing section 106 and outputs a response signal (ACKsignal or NACK signal) as the decoding result to retransmission controlsection 112.

PDCCH receiving section 110 performs blind decoding of the PDCCH signalreceived as input from demultiplexing section 106. Here, a PDCCH signalis placed in each of the plurality of downlink component bands. PDCCHreceiving section 110 decides a PDCCH signal of CRC=OK (no error)obtained by demasking CRC bits of the PDCCH signal received as inputfrom demultiplexing section 106 by the terminal ID of the subjectterminal, as a PDCCH signal for that terminal. Then, PDCCH receivingsection 110 obtains downlink resource allocation information and uplinkresource allocation information included in the PDCCH signal for thesubject terminal, outputs the downlink resource allocation informationto PDSCH receiving section 111 and outputs the uplink resourceallocation information to frequency mapping section 115 and resourcecontrol section 108.

PDSCH receiving section 111 extracts the PDSCH signal received as inputfrom demultiplexing section 106, based on the downlink resourceallocation information received as input from PDCCH receiving section110.

Retransmission control section 112 controls retransmission oftransmission data according to a response signal (ACK signal or NACKsignal) received as input from PHICH receiving section 109. To be morespecific, upon receiving an ACK signal of base station 200 from PHICHreceiving section 109, retransmission control section 112 commandsmodulating section 113 to modulate new transmission data. In contrast,upon receiving a NACK of base station 200 from PHICH receiving section109, that is, upon retransmission, retransmission control section 109commands modulating section 113 to modulate transmission data(retransmission data) for the NACK signal.

Modulating section 113 modulates transmission data (new transmissiondata or retransmission data) according to the command fromretransmission control section 112, and outputs the resulting modulationsignal to DFT (Discrete Fourier Transform) section 114.

DFT section 114 transforms the modulation signal received as input frommodulating section 113 into the frequency domain and outputs a pluralityof resulting frequency components to frequency mapping section 115.

Frequency mapping section 115 maps the plurality of frequency componentsreceived as input from DFT section 114 on a PUSCH placed on an uplinkcomponent band, according to the uplink resource allocation informationreceived as input from PDCCH receiving section 110.

IFFT (Inverse Fast Fourier Transform) section 116 transforms the mappedfrequency components into a time domain waveform and CP attachingsection 117 attaches a CP to the time domain waveform.

RF transmitting section 118 performs radio transmission processing (suchas up-conversion and digital-to-analog (D/A) conversion) on the signalwith a CP and transmits the result via antenna 101.

FIG. 4 is a block diagram showing a configuration of base station 200according to the present embodiment. Base station 200 is an LTE+ basestation.

Control section 201 generates uplink resource allocation information anddownlink resource allocation information, outputs the uplink resourceallocation information to PDCCH generating section 202 and extractingsection 217, and outputs the downlink resource allocation information toPDCCH generating section 202 and multiplexing section 209. Here, controlsection 201 assigns the uplink resource allocation information anddownlink resource allocation information to PDCCH's placed in respectivedownlink component bands.

Also, control section 201 assigns a response signal for uplink data toPHICH's placed in downlink bands which are a same number of partialdownlink component bands as the number of uplink bands among theplurality of downlink component bands. To be more specific, controlsection 201 assigns a response signal for uplink data to a PHICH placedin an LTE/LTE+ coexisting band among the plurality of downlink componentbands, regardless of whether the transmission source terminal of theuplink data is an LTE terminal or the transmission source terminal is anLTE+ terminal. Also, control section 201 specifies the PHICH resourcenumber associated with the RB number of a PUSCH to which the uplink datafrom the terminal is assigned. Then, control section 201 generates PHICHresource information indicating the PHICH resource number and downlinkcomponent band in which a response signal for the uplink data of thatterminal, and outputs this PHICH resource information to PHICH placingsection 208.

PDCCH generating section 202 generates a PDCCH signal including theuplink resource allocation information and downlink resource allocationinformation received as input from control section 201. Also, PDCCHgenerating section 202 attaches CRC bits to the PDCCH signal to whichthe uplink resource allocation information and downlink resourceallocation information are assigned, and, furthermore, masks the CRCbits by the terminal ID. Then, PDCCH generating section 202 outputs themasked PDCCH signal to modulating section 203.

Modulating section 203 modulates the PDCCH signal received as input fromPDCCH generating section 202 and outputs the modulated PDCCH signal tomultiplexing section 209.

Depending on an error detection result (as to whether or not there iserror) received as input from CRC section 220, response signalgenerating section 204 generates an ACK signal when CRC=OK (no error) ora NACK signal when CRC=NG (error present). Then, response signalgenerating section 204 outputs the generated response signal (ACK signalor NACK signal) to modulating section 205.

Modulating section 205 modulates the response signal received as inputfrom response signal generating section 204 and outputs the modulatedresponse signal to multiplexing section 209.

Modulating section 206 modulates input transmission data (downlink data)and outputs the modulated transmission data to multiplexing section 209.

SCH/BCH generating section 207 generates and outputs an SCH and BCH tomultiplexing section 209.

PHICH placing section 208 determines the PHICH placed in each downlinkcomponent band, based on the PHICH resource information received asinput from control section 201. To be more specific, PHICH placingsection 208 determines the PHICH, which is placed in the downlinkcomponent band indicated by the PHICH resource information and which isassociated with the PHICH resource number indicated by the PHICHresource information, as the PHICH placed in each component band. Then,PHICH placing section 208 outputs placement information indicating thedetermined PHICH placement, to multiplexing section 209.

Multiplexing section 209 multiplexes the PDCCH signal received as inputfrom modulating section 203, the response signal (i.e., PHICH signal)received as input from modulating section 205, the data signal (i.e.,PDSCH signal) received as input from modulating section 206 and the SCHand BCH received as input from SCH/BCH generating section 207. Here,multiplexing section 209 maps the data signal (PDSCH signal) on downlinkcomponent bands based on the downlink resource information received asinput from control section 201, and maps the response signal (PHICHsignal) on the downlink component bands based on the placementinformation received as input from PHICH placing section 208.

IFFT section 210 transforms the multiplex signal into a time domainwaveform and CP attaching section 211 obtains an OFDM signal byattaching a CP to this time domain waveform.

RF transmitting section 212 performs radio transmission processing (suchas up-conversion and digital-to-analog (D/A) conversion) on the OFDMsignal received as input from CP attaching section 211 and transmits theresult via antenna 213. By this means, an OFDM signal including resourceallocation information or response signal is transmitted.

In contrast, RF receiving section 214 performs radio receptionprocessing (such as down conversion and analog-to-digital (A/D)conversion) on a radio reception signal received in a reception band viaantenna 213, and outputs the resulting reception signal to CP removingsection 215.

CP removing section 215 removes a CP from the reception signal and FFTsection 26 transforms the reception signal without a CP into a frequencydomain signal.

Extracting section 217 extracts uplink data from the frequency domainsignal received as input from FFT section 216, based on the uplinkresource allocation information received as input from control section201, and IDFT (Inverse Discrete Fourier Transform) section 218transforms the extracted signal into a time domain signal and outputsthis time domain signal to data receiving section 219.

Data receiving section 219 decodes the time domain signal received asinput from IDFT section 218. Then, data receiving section 219 outputsthe decoded uplink data as reception data and also outputs this data toCRC section 220.

CRC section 220 performs error detection of the decoded uplink datausing CRC and outputs the error detection result (CRC=OK (no error) orCRC=NG (error present)) to response signal generating section 204.

Next, operations of terminal 100 and base station 200 will be explainedin detail.

Base station 200 transmits a PHICH and PDCCH in the frequency positionsas shown in the upper part of FIG. 5. As shown in FIG. 5, base station200 can perform communication using two downlink component bands(LTE/LTE+ coexisting band and LTE+ band) and one uplink component band(LTE/LTE+ coexisting band). Here, as shown in the upper part of FIG. 5,PDCCH's are placed in two downlink component bands, respectively. Incontrast, a PHICH is placed only in a same number of partial downlinkcomponent bands as the number of uplink component bands (i.e., one)among the two downlink component bands. To be more specific, as shown inthe upper part of FIG. 5, a PHICH is placed in the LTE/LTE+ coexistingband in which both the LTE terminal and LTE+ terminal can performcommunication. That is, the PHICH is placed in the LTE/LTE+ coexistingband in which an SCH and BCH are placed.

Also, the BCH includes information related to the number of OFDM symbolsin which the PHICH is placed and information related to the number ofresources for the PHICH. Here, assume that the number of OFDM symbols inwhich the PHICH is placed has two patterns (i.e., one symbol and threesymbols). Therefore, the number of OFDM symbols placed in the PHICH isincluded in the BCH as one-bit information. Also, for convenience, thenumber of PHICH resources is reported in association with the number ofRB's included in the downlink component band. To be more specific, thenumber of PHICH resources is twice, one time, half or quarter of thenumber of RB's included in the downlink component band. Also, if aplurality of RB's are used to transmit uplink data, terminal 100 andbase station 200 decide that a response signal is assigned to the PHICHassociated with the RB of the minimum RB number among the plurality ofRB's used to transmit the uplink data.

First, a case will be explained where base station 200 (LTE+ basestation) and terminal 100 (type-2 LTE+ terminal) perform communication.

First, control section 201 of base station 200 assigns uplink resourceallocation information and downlink resource allocation information tobe reported to terminal 100, to one of PDCCH's placed in the LTE/LTE+coexisting band and LTE+ band shown in the upper part of FIG. 5.

Demultiplexing section 106 of terminal 100 demultiplexes the PDCCHsignals placed in the LTE/LTE+ coexisting band and LTE+ band shown inthe upper part of FIG. 5, from reception signals, and PDCCH receivingsection 110 obtains resource allocation information (uplink resourceallocation information and downlink resource allocation information) forthe subject terminal from the demultiplexed PDCCH signals. Then,according to the obtained uplink resource allocation information,frequency mapping section 115 of terminal 100 maps transmission data onthe PUSCH placed in the uplink component band (LTE/LTE+ coexisting band)shown in the lower part of FIG. 5.

Next, response signal generating section 204 of base station 200generates a response signal (ACK signal or NACK signal) for uplink datafrom terminal 100. Also, control section 201 of base station 200 assignsa response signal for the uplink data of terminal 100 to the PHICHplaced in the LTE/LTE+ coexisting band shown in the upper part of FIG.5. Here, control section 201 specifies the PHICH resource number of thePHICH resource number associated with the RR number of the PUSCHassigned to the uplink data, from the PHICH placed in the LTE/LTE+coexisting band shown in the upper part of FIG. 5.

That is, as shown in FIG. 5, regardless of whether the PDCCH to whichuplink resource allocation information for terminal 100 is assigned isthe PDCCH placed in the LTE/LTE+ coexisting band or the PDCCH placed inthe LTE+ band, control section 201 of base station 200 assigns aresponse signal to the PHICH placed in the LTE/LTE+ coexisting band. Forexample, as shown in FIG. 5, even in a case where base station 200transmits resource allocation information using the PDCCH placed in theLTE+ band, control section 201 assigns a response signal for uplink datatransmitted according to the resource allocation information, to thePHICH placed in the LTE/LTE+ coexisting band.

Also, control section 108 of terminal 100 selects the LTE/LTE+coexisting band from the two downlink component bands, as a downlinkcomponent band to which the response signal for the uplink data isassigned. That is, as shown in FIG. 5, regardless of whether the PDCCHto which uplink resource allocation information for the subject terminalis assigned is the PDCCH placed in the LTE/LTE+ coexisting band or thePDCCH placed in the LTE+ band, similar to control section 201 of basestation 200, resource control section 108 performs control so as toextract the response signal for the uplink data from the PHICH placed inthe LTE/LTE+ coexisting band. Further, resource control section 108calculates the PHICH resource number of the PHICH associated with the RBnumber of the PUSCH on which the uplink data is mapped. Further,demultiplexing section 106 extracts the response signal for the uplinkdata from the PHICH which is placed in the downlink component band(LTE/LTE+ coexisting band) selected in resource control section 108 andwhich has the PHICH resource number calculated in resource controlsection 108.

In contrast, upon communicating with a terminal that can performcommunication using only one component band (i.e., LTE terminal ortype-1 LTE+ terminal), base station 200 (LTE+ base station) includes theLTE terminal and type-1 LTE+ terminal in the LTE/LTE+ coexisting band.Therefore, the LTE terminal or the type-1 LTE+ terminal receivesresource allocation information assigned to the PDCCH placed in theLTE/LTE+ coexisting band and transmits uplink data (PUSCH signal) tobase station 200 according to the resource allocation information. Then,the LTE terminal or the type-1 LTE+ terminal extracts a response signalfor the uplink data from the PHICH placed in the LTE/LTE+ coexistingband. That is, the LTE terminal or the type-1 LTE+ terminal communicateswith base station 200 always using the LTE/LTE+ coexisting band.

Thus, among a plurality of downlink component bands, a downlinkcomponent band in which an SCH and BCH are placed, that is, a downlinkcomponent band in which both an LTE terminal and LTE+ terminal canperform communication, is used as a partial downlink component band inwhich a PHICH is placed. By this means, all terminals (LTE terminal,type-1 LTE+ terminal and type-2 LTE+ terminal (terminal 100)) supportedby an LTE+ terminal (base station 200) receive a response signalassigned to the PHICH placed in the LTE/LTE+ coexisting band. That is,all terminals supported by the LTE+ system can receive the same PHICH.Therefore, a PHICH needs not be placed in the LTE+ band, so that it ispossible to reduce the PHICH overhead. Further, since a PHICH needs notbe placed in the LTE+ band, it is possible to place more PDSCH's andimprove the use efficiency of frequency.

Also, PDCCH's are placed in both the LTE/LTE+ coexisting band and LTE+band. Consequently, by using PDCCH's placed in respective downlinkcomponent bands, base station 200 can efficiently assign PDSCH's placedin two respective component bands and a PUSCH placed in one uplinkcomponent band to each terminal.

As described above, according to the present embodiment, an LTE+ basestation assigns uplink resource allocation information and downlinkresource allocation information to PDCCH's placed in respective downlinkcomponent bands, and assigns a response signal for uplink data to aPHICH placed in downlink component bands which are a same number ofpartial downlink component bands as the number of uplink component bandsamong the plurality of downlink component bands. By this means, the LTE+base station can transmit PHICH's and PDCCH's required for the LTEterminal and LTE+ terminal, with placement of high use efficiency offrequency. Therefore, according to the present embodiment, it ispossible to improve the use efficiency of frequency in a case wherecommunication bandwidths are asymmetric between uplink and downlink.

Embodiment 2

A case will be explained with the present embodiment where a type-1 LTE+terminal performs communication in an LTE+ band. Also, the basicconfigurations of a terminal and base station according to the presentembodiment are the same as the configuration of the terminal and basestation explained in Embodiment 1. Therefore, the terminal according tothe present embodiment will be explained using FIG. 3 and also FIG. 4.

Base station 200 according to the present embodiment transmits PHICH'sand PDCCH's in frequency placement as shown in the upper part of FIG. 6.As shown in FIG. 6, similar to FIG. 5 of Embodiment 1, base station 200can perform communication using two downlink component bands (LTE/LTE+coexisting band and LTE+ band) and one uplink component band (LTE/LTE+coexisting band). Here, as shown in the upper part of FIG. 6, PHICH'sare placed in the downlink component bands of the LTE/LTE+ coexistingband and LTE+ band. Here, as shown in the upper part of FIG. 6, theamount of resources for the PHICH placed in the LTE/LTE+ coexisting bandis larger than the amount of resources for the PHICH placed in the LTE+band. To be more specific, while the amount of resources for the PHICHplaced in the LTE/LTE+ coexisting band is the same as in Embodiment 1(upper part of FIG. 5), the amount of resources for the PHICH placed inthe LTE+ band is smaller than the amount of resources for the PHICHplaced in the LTE/LTE+ coexisting band.

Also, the amount of resources for the PHICH placed in the LTE+ band isassociated in advance with the amount of resources for the PHICH placedin the LTE/LTE+ coexisting band. For example, the amount of resourcesfor the PHICH placed in the LTE+ band is half the amount of resourcesfor the PHICH placed in the LTE/LTE+ coexisting band.

Also, as shown in the upper part of FIG. 6, similar to Embodiment 1,PDCCH's are placed in two downlink component bands, respectively, and anSCH/BCH is placed only in the LTE/LTE+ coexisting band.

Also, operations of the LTE terminal and the type-1 LTE+ terminal andtype-2 LTE+ terminal (terminal 100) included in the LTE/LTE+ coexistingband shown in the upper part of FIG. 6, are the same as in Embodiment 1.That is, these terminals each receive a response signal placed in thePHICH placed in the LTE/LTE+ coexisting band shown in the upper part ofFIG. 6.

Therefore, a case will be explained below where base station 200 (LTE+base station) and the type-1 LTE+ terminal included in the LTE+ bandshown in the upper part of FIG. 6 perform communication.

First, the type-1 LTE+ terminal (i.e., a terminal that can performcommunication using only one component band) is included in the LTE/LTE+coexisting band, receives an SCH/BCH placed in the LTE/LTE+ coexistingband and access base station 200. Next, base station 200 commands thetype-1 LTE+ terminal to move from the LTE/LTE+ coexisting band to theLTE+ band, and the type-1 LTE+ terminal moves to the LTE+ band accordingto the command from base station 200. By this means, the type-1 LTE+terminal is included in the LTE+ band.

Here, the type-1 LTE+ terminal obtains PHICH resource information (e.g.,an OFDM symbol in which a PHICH is placed or the number of PHICHresources) in the LTE/LTE+ coexisting band, indicated by the BCH placedin the LTE/LTE+ coexisting band. Then, the type-1 LTE+ terminalcalculates resource information for the PHICH, placed in the LTE+ band,based on the association between the PHICH placed in the LTE/LTE+coexisting band and the PHICH placed in the LTE+ band. For example, thetype-1 LTE+ terminal calculates a half of the number of resources forthe PHICH placed in the LTE/LTE+ coexisting band, as the number ofresources for the PHICH placed in the LTE+ band.

Then, the type-1 LTE+ terminal receives resource allocation informationassigned to the PDCCH placed in the LTE+ band shown in the upper part ofFIG. 6, and transmits uplink data (PUSCH signal) to base station 200according to the resource allocation information.

Control section 201 of base station 200 performs perform control toassign a response signal for uplink data of the type-1 LTE+ terminal tothe PHICH placed in the LTE+ band among two downlink component bandsshown in the upper part of FIG. 6. That is, as shown in FIG. 6, basestation 200 assigns a response signal for uplink data of the type-1 LTE+terminal included in the LTE+ band, to the PHICH placed in the LTE+band. Also, similar to base station 200, the type-1 LTE+ terminalextracts the response signal for the uplink data from the PHICH placedin the LTE+ band.

Thus, a PHICH is placed in the LTE+ band shown in FIG. 6, so that it ispossible to include the type-1 LTE+ terminal in the LTE+ band.Therefore, when included in the LTE+ band, the type-1 LTE+ terminalreceives the response signal assigned to the PHICH placed in the LTE+band. In contrast, similar to Embodiment 1, the LTE terminal and type-2LTE+ terminal (terminal 100) receive the PHICH placed in the LTE/LTE+coexisting band. That is, the PHICH placed in the LTE+ band is used onlyin the type-1 LTE+ terminal included in the LTE+ band.

Here, the PHICH placed in the LTE+ band is associated with the samePUSCH as the PUSCH associated with the PHICH placed in the LTE/LTE+coexisting band. However, as described above, the amount of resourcesfor the PHICH placed in the LTE+ band is smaller than the amount ofresources for the PHICH placed in the LTE/LTE+ coexisting band, so thatit is possible to reduce the PHICH overhead in the LTE+ band. Also, inthe LTE+ band, by making the amount of PHICH resources smaller than theamount of resources for the PHICH placed in the LTE/LTE+ coexistingband, it is possible to place more PDSCH's.

As described above, according to the present embodiment, even in a casewhere the type-1 LTE+ terminal is included in the LTE+ band, similar toEmbodiment 1, it is possible to improve the use efficiency of frequency.Further, according to the present embodiment, when included in the LTE+band, the type-1 LTE+ terminal calculates PHICH resource information inthe LTE+ band based on PHICH resource information in the LTE/LTE+coexisting band. By this means, the base station does not requiresignaling of PHICH resource information in the LTE+ band, so that it ispossible to further improve the use efficiency of frequency.

Also, a case has been described above with the present embodiment whereresource information of a PHICH placed in an LTE+ band is associatedwith resource information of a PHICH placed in an LTE/LTE+ coexistingband. However, with the present invention, resource information of thePHICH placed in the LTE+ band may be reported using a BCH in theLTE/LTE+ coexisting band, or may be reported separately to the type-1LTE+ terminal included in the LTE+ band.

Also, a case has been described above with the present embodiment where,in the same way as in Embodiment 1, a type-2 LTE+ terminal selects aPHICH placed in a downlink component band (LTE/LTE+ coexisting band) inwhich an SCH/BCH is placed, from a plurality of downlink componentbands. However, with the present invention, an LTE+ base station maycommand the type-2 LTE+ terminal separately as to whether to select thePHICH placed in the LTE/LTE+ coexisting band or a PHICH placed in theLTE+ band. By this means, even in a case where an SCH/BCH is placed inall downlink component bands, the type-2 LTE+ terminal can specify adownlink component band in which a PHICH assigned a response signal isplaced, so that it is possible to provide the same effect as in thepresent invention.

Embodiment 3

Similar to Embodiment 1, when communication bandwidths (the number ofcomponent bands) are asymmetric between uplink and downlink, a case willbe explained with the present embodiment where PHICH resources areplaced only in one component band and uplink resource allocationinformation of uplink data is transmitted to terminals by a PDCCH onlyin a partial downlink component band in which PHICH resources areplaced.

Also, downlink resource allocation information and uplink resourceallocation information of the downlink component band in which PHICHresources are placed, have the same information size (i.e., the numberof bits required for transmission). Also, a PDCCH signal includes typeinformation of resource allocation information (e.g., one-hit flag).Therefore, even if a PDCCH signal including downlink resource allocationinformation and a PDCCH signal including uplink resource allocationinformation are the same size, by identifying type information ofresource allocation information, it is possible to distinguish betweendownlink resource allocation information and uplink resource allocationinformation. Also, the PDCCH format upon transmitting uplink resourceallocation information is PDCCH format 0, and the PDCCH format upontransmitting downlink resource allocation information is PDCCH format1A.

In contrast, if the uplink bandwidth and the downlink bandwidth aredifferent, the information size is different between downlink resourceallocation information and uplink resource allocation information. Withthe present embodiment, if the information size of downlink resourceallocation information and the information size of uplink resourceallocation information are different due to such a bandwidth difference,by attaching zero information (zero padding) to resource allocationinformation assigned to a PDCCH in a partial downlink component band,the information size of downlink resource allocation information and theinformation size of uplink resource allocation information are madeequal. By this means, regardless of downlink resource allocationinformation and uplink resource allocation information, the PDCCH signalsize is maintained the same.

The components of terminal 800 according to Embodiment 3 of the presentinvention will be explained using FIG. 7.

FIG. 7 is a block diagram showing a configuration of terminal 800according to Embodiment 3 of the present invention. Terminal 800 shownin FIG. 7 employs a configuration adding format deciding section 803 andreplacing PDCCH receiving section 110 with PDCCH receiving section 802and broadcast information receiving section 107 with broadcastinformation receiving section 801 in terminal 100 according toEmbodiment 1 shown in FIG. 3. Also, in FIG. 7, the same components as inFIG. 3 will be assigned the same reference numerals and theirexplanation will be omitted.

Based on frame synchronization timing information received as input fromframe synchronization section 105, demultiplexing section 106demultiplexes a signal received as input from frame synchronizationsection 105 into the BCH, response signal (i.e., PHICH signal), controlsignal (i.e., PDCCH signal) and data signal (i.e., PDSCH signal). Here,upon receiving the PHICH signal, demultiplexing section 106 extracts aresponse signal for uplink data of the subject terminal from thedemultiplexed PHICH signal, according to a downlink component band andPHICH resource number indicated by resource control information receivedas input from resource control section 108. That is, demultiplexingsection 106 extracts a response signal for uplink data of the subjectterminal from a PHICH placed in LTE/LTE coexisting bands which are asame number of partial downlink component bands as the number of uplinkcomponent bands among a plurality of downlink component bands and inwhich an SCH/BCH is placed. Then, demultiplexing section 106 outputs theBCH to broadcast information receiving section 801, the PHICH signal toPHICH receiving section 109, the PDCCH signal to PDCCH receiving section802 and the PDSCH signal to PDSCH receiving section 111.

Broadcast information receiving section 801 reads the content of the BCHreceived as input from demultiplexing section 106, associates the RBnumber of the PUSCH and the PHICH resource number of the PHICH, andobtains PHICH resource information indicating the number of PHICHresources. Then, broadcast information receiving section 801 outputs thePHICH resource information to resource control section 108. Also,broadcast information receiving section 801 reads the content of the BCHreceived as input from demultiplexing section 106 and obtains BCHinformation related to formats of downlink component bands and uplinkcomponent band of base station 900 (described later). Broadcastinformation receiving section 801 obtains, for example, the number ofuplink component bands, the number of downlink bands, the identificationnumber and bandwidth of each component band, information associating theuplink bands and downlink bands, and reference component bandinformation. Also, although the reference component band can be foundfrom the bandwidth of an uplink component band and the bandwidth of adownlink component band, base station 900 includes identificationinformation of the reference component band in a BCH in this case. Then,broadcast information receiving section 801 outputs the obtained BCHinformation to format deciding section 803 and PDCCH receiving section802.

PDCCH receiving section 802 performs blind decoding of the PDCCH signalin each downlink component band, received as input from demultiplexingsection 106, using the information size of resource allocationinformation supporting the bandwidth of each downlink component band,the information size of resource allocation information supporting thebandwidth of the uplink component band and the terminal ID of thesubject terminal. Here, PDCCH signals are placed in the plurality ofdownlink component bands, respectively.

That is, first, PDCCH receiving section 802 specifies the CRC bitcorresponding part, included in each PDCCH signal. At this time, a caseis possible where base station 900 adjusts the information size by zeropadding. Therefore, PDCCH receiving section 802 specifies the CRC bitcorresponding part in the PDCCH signal of the reference component band,using the information size (payload size) found from the wider bandwidthbetween the bandwidth of the reference component band and the bandwidthof the uplink component band associated with that reference componentband. In contrast, only downlink resource allocation information isincluded in downlink component bands other than the reference componentband. Therefore, PDCCH receiving section 802 specifies the CRC bitcorresponding part in downlink component bands other than the referencecomponent band, using the information size based on the bandwidths ofthe downlink component bands. Also, PDCCH receiving section 802 decidesa PDCCH signal of CRC=OK (no error) obtained by demasking CRC bits ofthe PDCCH signal received as input from demultiplexing section 106 bythe terminal ID of the subject terminal, as a PDCCH signal for thatterminal. Thus, the PDCCH signal decided for the subject terminal isoutputted to format deciding section 803. Also, the reference componentband will be described later.

Based on type information of resource allocation information included inthe PDCCH signal received as input from PDCCH receiving section 802,format deciding section 803 decides whether the format of the PDCCHsignal is “format 0” or “format 1A.” Upon deciding format 0, formatdeciding section 803 outputs uplink resource allocation informationincluded in the PDCCH signal to frequency mapping section 115 andresource control section 108. Also, upon deciding format 1A, formatdeciding section 803 outputs downlink resource allocation informationincluded in the PDCCH signal to PDSCH receiving section 111. At thistime, uplink resource allocation information is not assigned to a PDCCHof a component band in which PHICH resources are not placed, and,consequently, format deciding section 803 decides format 0 in thecomponent band in which the PHICH resources are not placed.

Resource control section 108 specifies a PHICH to which a responsesignal for uplink data of the subject terminal is assigned, based on thePHICH resource information received as input from broadcast informationreceiving section 801 and the uplink resource information received asinput from format deciding section 803. Here, a PHICH is placed in apartial component band among a plurality of downlink component bands.Therefore, resource control section 108 specifies the downlink componentband in which the PHICH is placed, based on the PHICH resourceinformation. Further, resource control section 108 specifies the PHICHresource number of the PHICH associated with the RB number of a PUSCHused to transmit uplink data of the subject terminal, based on theuplink resource allocation information. Then, resource control section108 outputs resource control information indicating the specifieddownlink component band and PHICH resource number of the PHICH, todemultiplexing section 106.

PDSCH receiving section 111 extracts reception data from the PDSCHsignal received as input from demultiplexing section 106, based on thedownlink resource allocation information received as input from formatdeciding section 803.

Frequency mapping section 115 maps the plurality of frequency componentsreceived as input from DFT section 114 on the PUSCH placed in the uplinkcomponent band, according to the uplink resource allocation informationreceived as input from format deciding section 803.

Next, a configuration of base station 900 according to Embodiment 3 ofthe present invention will be explained using FIG. 8. FIG. 8 is a blockdiagram showing a configuration of base station 900 according toEmbodiment 3 of the present invention.

Base station 900 shown in FIG. 8 employs a configuration adding paddingsection 903 and replacing control section 201 with control section 901and PDCCH generating section 202 with PDCCH generating section 902 inbase station 200 according to Embodiment 1 shown in FIG. 4. Also, inFIG. 8, the same components as in FIG. 4 will be assigned the samereference numerals and their explanation will be omitted.

Control section 901 generates uplink resource allocation information anddownlink resource allocation information, outputs the uplink resourceallocation information to PDCCH generating section 902 and extractingsection 217, and outputs the downlink allocation information to PDCCHgenerating section 902 and multiplexing section 209. Control section 901assigns the downlink resource allocation information to all of aplurality of downlink component bands, while assigning the uplinkresource allocation information only to part of the plurality ofdownlink component bands. Here, especially, among the plurality ofdownlink component bands associated with one uplink component band, theuplink resource allocation information is assigned to the downlinkcomponent band having the closest bandwidth to the bandwidth of theuplink component band. Here, an assignment target downlink componentband to which uplink resource allocation information is assigned, may becalled “reference component band.”

Control section 901 outputs the uplink resource allocation informationand downlink resource allocation information to PDCCH generating section902 and outputs information related to the reference component band(which may be referred to as “reference component band information”) toPDCCH generating section 902. Here, this reference component bandinformation may be included in a BCH in SCH/BCH generating section 207.

Also, control section 901 outputs bandwidth comparison informationindicating which of the bandwidths of the reference component band anduplink component band is larger, to padding section 903 via PDCCHgenerating section 902.

Also, control section 901 assigns a response signal for uplink data to aPHICH placed in a same number of partial component bands as the numberof uplink component bands, among a the plurality of downlink componentbands. To be more specific, control section 901 assigns a responsesignal for uplink data to a PHICH placed in the LTE/LTE+ coexisting bandamong the plurality of downlink component bands, regardless of whetheror not the transmission source terminal of the uplink data is an LTEterminal or LTE+ terminal. Also, control section 901 specifies the PHICHresource number associated with the RB number of a PUSCH to which theuplink data from the terminal is assigned. Then, control section 901generates PHICH resource information indicating the PHICH resourcenumber and the downlink component band in which the response signal forthe uplink data of the terminal is placed, and outputs this PHICHresource information to PHICH placing section 208.

PDCCH generating section 902 generates a PDCCH signal including theuplink resource allocation information and downlink resource allocationinformation from control section 901. At this time, PDCCH generatingsection 902 includes the uplink resource allocation information anddownlink resource allocation information in the PDCCH signal placed inthe downlink component band indicated by the reference component bandinformation, and includes only the downlink resource allocationinformation in PDCCH signals placed in other downlink component bands.Then, PDCCH generating section 902 outputs these PDCCH signals topadding section 903.

Padding section 903 attaches zero information (zero padding) to one ofthe downlink resource allocation information and uplink resourceallocation information with the smaller information size until theinformation sizes are equal, in the PDCCH signal received as input fromPDCCH generating section 902. At this time, padding section 903 does notattach zero information to downlink resource allocation information fora PDCCH placed in a downlink component band in which PHICH resources arenot placed, and attaches zero information only to downlink resourceallocation information or uplink resource allocation information for aPDCCH placed in a downlink component band in which PHICH resources areplaced. Also, padding section 903 decides to which of downlink resourceallocation information and uplink resource allocation information zeroinformation is attached, based on the bandwidth comparison INFORMATION.Also, padding section 903 attaches CRC bits to the PDCCH signal to whichthe uplink resource allocation information and downlink resourceallocation information are assigned, and masks the CRC bits by theterminal ID. Then, padding section 903 outputs the PDCCH signal with CRCbits to modulating section 203.

Modulating section 203 modulates the PDCCH signal received as input frompadding section 903 and outputs the modulated PDCCH signal tomultiplexing section 209.

Next, operations of terminal 800 and base station 900 will be explainedusing FIG. 9. FIG. 9 shows an example of placing a PHICH and PDCCH.

Base station 900 places PHICH resources only in a partial component bandof a plurality of downlink component bands, and transmits uplinkresource allocation information of uplink data using a PDCCH only fromthe partial component band in which PHICH resources are placed. That is,base station 900 does not use PDCCH resources for transmitting uplinkresource allocation information of uplink data in a component band inwhich PHICH resources are not placed.

Also, similar to above Embodiment 1, PDCCH receiving section 802 ofterminal 800 performs blind decoding of a PDCCH signal received as inputfrom demultiplexing section 106. The size of PDCCH information bitsrequired for blind decoding is determined by a decision result as towhether or not PHICH resources are placed in a component band in whichthe PDCCH is transmitted, and by the bandwidth of the uplink componentband associated with the downlink component band in which PDCCHresources are transmitted.

That is, in a downlink component band in which PHICH resources are notplaced, the information size used for blind decoding of PDCCH isdetermined only by the bandwidth of the downlink component band.

By contrast with this, in a downlink component band in which PHICHresources are placed, the information size used for blind decoding ofPDCCH is determined with reference to the wider bandwidth between thebandwidth of the downlink component band and the bandwidth of the uplinkcomponent band. To be more specific, when component band frequency issmaller, the number of bits required to indicate the frequency positionof assigned link resources is small. Consequently, for example, when theuplink component band is larger than the downlink component band, it isdecided that “0” is inserted (zero padding) in downlink resourceallocation information of downlink data. By this means, it is possibleto assume that uplink resource allocation information of uplink data anddownlink resource allocation information have the same information size.By this zero padding, the information size of uplink resource allocationinformation of uplink data and the information size of downlink resourceallocation information are the same, so that it is possible to try blinddecoding for these items of data at the same time and reduce the circuitscale of the terminal. Also, based on one-bit “uplink/downlinkallocation information decision flag” included in the information bits,it is possible to decide whether information with successful blinddecoding is uplink resource allocation information of uplink data ordownlink resource allocation information of downlink data.

Also, in zero padding, when the bandwidth is different between thedownlink component band on the higher-frequency side and the uplinkcomponent band, regarding this pair, zero information is attached todownlink resource allocation information with the smaller size until theinformation size of the downlink resource allocation information and theinformation size of uplink resource allocation information are the same.However, zero padding is performed for size adjustment, and,consequently, zero information contains no particular meaning. That is,a signal that is not essentially necessary is included in downlinkcontrol information, and, consequently, if the entire power is fixed,the power per information bit, which is essentially necessary, maydegrade.

Also, the importance level of downlink control information is generallyhigher than uplink control information. That is, this is becausedownlink control information is used to report not only resourceallocation information of downlink data channels but also schedulinginformation of other important information (e.g., paging information orbroadcast information). Therefore, it is desired that the frequency ofzero padding with respect to downlink control information becomes less.

Here, the frequency diversity effect obtained by PDCCH depends on thebandwidth of a downlink component band. Therefore, in a downlinkcomponent band of a narrower bandwidth, the frequency diversity effectis small, and, consequently, factors to degrade the quality are demandedto be removed as much as possible. However, regarding zero padding,there is a higher possibility of zero padding in a downlink componentband of a narrower bandwidth.

Such a situation cannot occur because a downlink frequency band islarger than an uplink frequency band in the LTE system not including theconcept of carrier aggregation. By contrast with this, in the LTE+system which adopts carrier aggregation and, furthermore, associates aplurality of downlink component bands with one uplink component band, asituation frequently occurs in which, if the whole downlink frequencybandwidth is wider than the uplink frequency bandwidth, a downlinkcomponent band is narrower than the uplink band, focusing on thecomponent bands.

Also, to avoid zero padding, a method of making the sizes differentbetween uplink control information and downlink control information ispossible. However, in this case, the terminal side needs to performblind decoding of two items of control information with differentinformation bits. Therefore, a problem arises that the number of timesof blind decoding increases and therefore the circuit scale increases.

By contrast with this, with the present embodiment, in a PDCCH placed ina downlink component band in which PHICH resources are not placed, onlydownlink resource allocation information of downlink data is assigned,and zero padding is not performed, so that it is possible to reducedegradation in essentially necessary power per information bit.

Thus, according to the present embodiment, in addition to the effect ofabove Embodiment 1, uplink resource allocation information is nottransmitted in a downlink component band in which PHICH resources arenot placed, it is possible to avoid zero padding performed to adjust theinformation size of resource allocation information of downlink data tothe information size of resource allocation information of uplink data.

By this means, unnecessary data transmission is not performed, so thatit is possible to improve essentially necessary power per informationbit.

Also, with the present embodiment, a terminal is designed to decidewhether or not zero padding is necessary upon performing blind decoding,based on whether or not PHICH resources are present, but, actually, anSCH and BCH for an LTE terminal to include LTE terminals are placed in acomponent band in which PHICH resources are present. Therefore, theterminal may decide whether or not zero padding is necessary, based onwhether or not an SCH/BCH to include LTE terminals is present.

Also, with the present embodiment, although zero padding to insert “0”is performed to make the information sizes equal, the present embodimentis not limited to this, and it is equally possible to make theinformation sizes equal by attaching an arbitrary redundant bitdifferent from “0.”

Also, with the present embodiment, format 0 is not decided in acomponent band in which PHICH resources are not placed, so that it ispossible to reduce type information bits of resource allocationinformation included in the PDCCH in a component band in which PHICHresources are not placed. That is, it is possible to improve the powerefficiency in PDCCH transmission. Also, if a part corresponding to thetype information bits is not reduced, a part corresponding to the typeinformation bits of resource allocation information adopts a fixed vale(i.e., type information indicating downlink assignment) in a componentband in which PHICH resources are not placed, so that the terminal sidecan use that part as a partial parity bit.

Embodiment 4

The present embodiment differs from Embodiment 3 only in that theinformation sizes may be different between downlink resource allocationinformation and uplink resource allocation information even in a casewhere the uplink bandwidth and the downlink bandwidth are equal.

That is, a case has been described above with Embodiment 3 where, if theuplink bandwidth and the downlink bandwidth are the same, theinformation sizes are the same between uplink resource allocationinformation and downlink resource allocation information in a downlinkcomponent band in which PHICH resources are placed. By contrast withthis, with the present embodiment, even if the uplink bandwidth and thedownlink bandwidth are the same, the information sizes are substantiallythe same but are not always the same between downlink resourceallocation information and uplink resource allocation information. Also,when the difference between the uplink bandwidth and the downlinkbandwidth becomes larger, the difference of information sizes betweendownlink resource allocation information and uplink resource allocationinformation becomes larger.

Therefore, with the present embodiment, to maintain the informationsizes the same between downlink resource allocation information anduplink resource allocation information, if the information sizes aredifferent between the downlink resource allocation information and theuplink resource allocation information, similar to Embodiment 3, zeroinformation is attached to resource allocation information assigned to aPDCCH in a partial downlink component band (0 padding).

The present embodiment will be explained below in detail.

Here, the basic configurations of a terminal and base station accordingto the present embodiment are the same as the configurations of theterminal and base station explained in Embodiment 3. Therefore, theterminal and base station according to the present embodiment will bealso explained using FIG. 7 and FIG. 8.

PDCCH receiving section 802 of terminal 800 (FIG. 7) according to thepresent embodiment performs blind decoding of the PDCCH signal in eachdownlink component band received as input from demultiplexing section106, using the information size of resource allocation informationsupporting the bandwidth of each downlink component band, theinformation size of resource allocation information supporting thebandwidth of the uplink component band and the terminal ID of thatterminal. Here, the PDCCH signal is placed in each of the plurality ofdownlink component bands.

That is, first, PDCCH receiving section 802 specifies the CRC bitcorresponding part included in each PDCCH signal. At this time, in basestation 900 (FIG. 8), the information size needs to be adjusted by zeropadding. Consequently, PDCCH receiving section 802 specifies the CRC bitcorresponding part in the PDCCH signal of the reference component band,using the larger information size (payload size) between the informationsize of downlink resource allocation information determined by thebandwidth of the reference component band and the information size ofuplink resource allocation information determined by the bandwidth ofthe uplink component band associated with the reference component band.In contrast, only downlink resource allocation information is includedin a downlink component band different from the reference componentband. Therefore, similar to Embodiment 3, PDCCH receiving section 802specifies the CRC bit corresponding part in a downlink component banddifferent from the reference component band, using the information sizecorresponding to the bandwidth of the downlink component band.

In contrast, control section 901 of base station 900 (FIG. 8) accordingto the present embodiment outputs, to padding section 903 via PDCCHgenerating section 902, information size comparison informationindicating the magnitude relationship between the information size ofdownlink resource allocation information determined by the bandwidth ofthe reference component band and the information size of uplink resourceallocation information determined by the bandwidth of the uplinkcomponent band.

Padding section 903 attaches zero information to information of thesmaller information size between the downlink resource allocationinformation and the uplink resource allocation information, in a PDCCHsignal received as input from PDCCH generating section 902, until thesesizes are equal (zero padding). At this time, padding section 903decides to which of the downlink resource allocation information anduplink resource allocation information zero information is attached,based on the information size comparison information.

Next, similar to Embodiment 3, operations of terminal 800 and basestation 900 will be explained using FIG. 9. FIG. 9 shows an example ofplacing a PHICH and PDCCH.

Similar to Embodiment 3, base station 900 places PHICH resources only ina partial downlink component band of a plurality of downlink componentbands, and transmits uplink resource allocation information of uplinkdata using a PDCCH only from the partial downlink component band inwhich the PHICH resources are placed. That is, base station 900 does notuse PDCCH resources to transmit uplink resource allocation informationof uplink data in a component band in which PHICH resources are notplaced. Therefore, PDCCH receiving section 802 of terminal 800 obtainsdownlink resource allocation information from each of the plurality ofdownlink component bands and obtains uplink resource allocationinformation from the partial downlink component band in which PHICHresources are placed.

Also, similar to above Embodiment 1, PDCCH receiving section 802 ofterminal 800 performs blind decoding of a PDCCH signal received as inputfrom demultiplexing section 106. The PDCCH information bit size requiredfor blind decoding is determined by: a decision result as to whether ornot PHICH resources are placed in a downlink component band to which aPDCCH is transmitted; the information size of downlink resourceallocation information determined by the bandwidth of the downlinkcomponent band in which PDCCH resources are placed; and the informationsize of uplink resource allocation information determined by thebandwidth of the uplink component band associated with the downlinkcomponent band.

That is, in a downlink component band in which PHICH resources are notplaced, PDCCH receiving section 802 determines the information size usedfor blind decoding of PDCCH, only by the information size of downlinkresource allocation information determined by the bandwidth of thedownlink component band.

By contrast with this, in a downlink component band in which PHICHresources are placed, PDCCH receiving section 802 determines theinformation size used for blind detection of PDCCH, with reference tothe larger information size between the information size of downlinkresource allocation information determined by the bandwidth of thedownlink component band and the information size of uplink resourceallocation information determined by the bandwidth of the uplinkcomponent band associated with the downlink component band. Here, whenthe bandwidth of a component band becomes narrower, the number of bitsrequired to indicate the frequency position of assigned link resourcesbecomes smaller. Therefore, for example, when the bandwidth of an uplinkcomponent band is wider than the bandwidth of a downlink component band,the information size of uplink resource allocation information is largerthan the information size of downlink resource allocation information inmost cases. Therefore, if the information size of uplink resourceallocation information is larger than the information size of downlinkresource allocation information, PDCCH receiving section 802 decidesthat “0” is inserted (zero padding) in the downlink resource allocationinformation. By this means, it is possible to presume that the uplinkresource allocation information and downlink resource allocationinformation have the same information size. By this zero padding, theinformation size of the uplink resource allocation information and theinformation size of the downlink resource allocation information are thesame, similar to Embodiment 3, terminal 800 can try blind decoding ofthese items of information at the same time, so that it is possible toreduce the circuit scale of the terminal. Also, it is possible to decidewhether information subjected to successful blind decoding is uplinkresource allocation information of uplink data or downlink resourceallocation information of downlink data, by one-bit “uplink/downlinkassignment information decision flag” included in the information bits.

Here, in a case where zero padding is performed, focusing on a pair of acertain downlink component band and uplink component band, if theinformation size of downlink resource allocation information determinedby the bandwidth of the downlink component band is smaller than theinformation size of uplink resource allocation information determined bythe bandwidth of the uplink component band, regarding this pair, zeroinformation is attached to the downlink resource allocation informationof the smaller information size until the information size of thedownlink resource allocation information and the information size of theuplink resource allocation information are equal. However, zero paddingis performed for size adjustment, and, consequently, zero informationcontains no particular meaning. That is, a signal that is notessentially necessary is included in downlink control information, and,consequently, if the entire power is fixed, the power per informationbit, which is essentially necessary, may degrade.

Also, the importance level of downlink control information is generallyhigher than uplink control information. This is because downlink controlinformation is used to report not only resource allocation informationof downlink data channels but also scheduling information of otherimportant information (e.g., paging information or broadcastinformation). Therefore, it is desired that the frequency of zeropadding with respect to downlink control information becomes less.

Here, the frequency diversity effect obtained by PDCCH depends on thebandwidth of a downlink component band. Therefore, in a downlinkcomponent band of a narrower bandwidth, the frequency diversity effectis small, and, consequently, factors to degrade the quality are demandedto be removed as much as possible. However, regarding zero padding,there is a higher possibility of zero padding in a downlink componentband of a narrower bandwidth.

Such a situation cannot occur because a downlink frequency band islarger than an uplink frequency band in the LTE system not including theconcept of carrier aggregation. By contrast with this, in the LTE+system which adopts carrier aggregation and, furthermore, associates aplurality of downlink component bands with one uplink component band, asituation frequently occurs in which, if the whole downlink frequencybandwidth is wider than the uplink frequency bandwidth, a downlinkcomponent band is narrower than the uplink band, focusing on thecomponent bands.

Also, to avoid zero padding, a method of making the sizes differentbetween uplink control information and downlink control information ispossible. However, in this case, the terminal side needs to performblind decoding of two items of control information with differentinformation bits. Therefore, a problem arises that the number of timesof blind decoding increases and therefore the circuit scale increases.

By contrast with this, with the present embodiment, similar toEmbodiment 3, only downlink resource allocation information of downlinkdata is assigned and zero padding is not performed in a PDCCH placed ina downlink component band in which PHICH resources are not placed, sothat it is possible to control the decrease in essentially necessarypower per information bit.

By this means, according to the present embodiment, similar toEmbodiment 3, uplink resource allocation information is not transmittedin a downlink component band in which PHICH resources are not placed, sothat it is possible to avoid performing zero padding to match theinformation size of resource allocation information of downlink data tothe information size of resource allocation information of uplink data.By this means, transmission of unnecessary data is not performed, sothat it is possible to improve essentially necessary power perinformation bit.

Also, with the present embodiment, a terminal decides whether or notzero padding is necessary upon performing blind decoding, based onwhether or not PHICH resources are present, but, actually, an SCH andBCH for LTE terminals to include LTE terminals are assigned to acomponent band in which PHICH resources are present. Therefore, theterminal may decide whether or not zero padding is necessary, based onwhether or not an SCH/BCH to include LTE terminals is present.

Also, with the present embodiment, although zero padding to insert “0”is performed to make the information sizes the same, the presentembodiment is not limited to this, and it is equally possible to makethe information sizes the same by attaching arbitrary information bitsother than “0.”

Also, with the present embodiment, format 0 cannot be decided in acomponent band in which PHICH resources are not placed, so that it ispossible to reduce type information bits of resource allocationinformation included in a PDCCH, in a component band in which PHICHresources are not placed. That is, it is possible to improve the powerefficiency in PDCCH transmission. Also, in a case where a partcorresponding to the type information bits is not reduced, the typeinformation bit corresponding part of resource allocation informationhas a fixed value (i.e., type information indicating downlinkallocation) in a component band in which PHICH resources are not placed,so that it is possible to use this part as part of parity bits on theterminal side.

Embodiment 5

The present embodiment differs from Embodiment 1 in forming theasymmetric carrier aggregation between uplink and downlink everyterminal, using a pair of downlink component bands and a pair of uplinkcomponent bands.

For example, as shown in FIG. 10, a base station manages two downlinkcomponent bands and two uplink component bands.

However, taking into account the power consumption in transmission of aterminal and capability of an RF transmission circuit, the base stationsets two downlink component bands to one terminal in downlink (i.e., thereception band of the terminal) while setting only one uplink componentband to the terminal in uplink (i.e., the transmission band of theterminal).

Also, in FIG. 10, two downlink component bands and one uplink componentband on the lower frequency side (associated with solid lines shown inFIG. 10) are set in terminal 1, and the same two downlink componentbands as those of terminal 1 and one uplink component band on the higherfrequency side (associated with dotted lines shown in FIG. 10) are setin terminal 2.

That is, in terminal 1 and terminal 2 of FIG. 10, although the samedownlink component bands are set in downlink, respective uplinkcomponent bands are set in uplink.

In this case, if a base station transmits uplink resource allocationinformation using any of PDCCH's placed in the downlink component bands,each terminal transmits uplink data based on the RB number of a PUSCHcorresponding to uplink allocation information for that terminal, in theset uplink component band. That is each terminal receives a signaltransmitted using one of the two downlink component bands in downlinkwhile transmitting a signal using only one uplink component band inuplink.

Also, as shown in FIG. 10, when the number of component bands set ineach terminal varies between uplink and downlink (asymmetric), asdescribed above (in FIG. 1), one PUSCH resource may be associated with aplurality of PHICH resources placed in each downlink component band.

By this means, although PHICH resources may be wasted, it is possible toprevent the contention for PHICH resource and significant degradation inthe system capability.

However, as shown in FIG. 10, in a case where the numbers of componentbands set in each terminal are asymmetric between uplink and downlink,and where carrier aggregation is formed in which the position of theuplink component band set in each terminal varies, PUSCH resourcesplaced in the different uplink component bands may be associated withthe same PHICH resources. For example, in FIG. 10, PUSCH resourcesplaced in respective uplink component bands (on the lower frequency sideand the higher frequency side) set for terminal 1 and terminal 2, andPHICH resources placed in the same downlink component band set forterminal 1 and terminal 2, can be associated with each other and used.In this case, a state occurs where the same PHICH resources are usedbetween terminal 1 and terminal 2, that is, where the contention forPHICH resources is caused.

Here, in the LTE system, the number of uplink component bands and thenumber of downlink component bands set for one LTE terminal are bothone, and the symmetry is secured in the numbers of component bandsbetween uplink and downlink. Therefore, in the LTE system, it ispossible to always associate PUSCH resources and PHICH resources on aone-to-one basis. Therefore, to reduce the overhead of signalingrequired to report PHICH resources for terminals, PHICH resources andthe RB numbers of PUSCH's are associated. That is, in the LTE system,PUSCH resources placed in respective uplink component bands areassociated with PHICH resources placed in respective downlink componentbands. In other words, the contention for the same PUSCH resources isnot caused between PUSCH resources placed in respective uplink componentbands. Also, in the LTE system, information indicating the uplinkcomponent band associated with each downlink component band isbroadcasted to terminals using the BCH placed in each downlink componentband.

Therefore, with the present embodiment, an LTE+ terminal extracts aresponse signal for uplink data of that terminal, from a PHICH placed ina downlink component band in which a BCH to broadcast information(including the frequency position of an uplink component band and thefrequency bandwidth of the uplink component band) related to an uplinkcomponent band used by that terminal (i.e., uplink component band setfor that terminal) is placed, among a plurality of downlink componentbands.

This will be explained below in detail. Also, basic configurations of aterminal and base station according to the present embodiment are thesame as the configurations of the terminal and base station explained inEmbodiment 1. Therefore, the terminal according to the presentembodiment will also be explained using FIG. 3 and FIG. 4.

That is, terminal 100 (FIG. 3) according to the present embodiment is atype-2 LTE+ terminal and can perform communication using a plurality ofdownlink component bands at the same time. Also, base station 200 (FIG.4) according to the present embodiment is an LTE+ base station.

Also, as shown in FIG. 10, an SCH and BCH are placed in each downlinkcomponent band.

Upon receiving a PHICH signal, demultiplexing section 106 of terminal100 extracts a response signal for uplink data for that terminal fromthe demultiplexed PHICH signal, according to a downlink component bandand PHICH resource number indicated by resource control informationreceived as input from resource control section 108.

To be more specific, demultiplexing section 106 extracts a responsesignal for uplink data for that terminal from a PHICH placed in adownlink semi-reference component band for that terminal, among aplurality of downlink component bands. Here, a downlink semi-referencecomponent band is a downlink component band mapping a BCH thatbroadcasts information on an uplink component band in which the uplinkcomponent band is utilized by the subject terminal by mapping uplinkdata of the subject terminal. Then, demultiplexing section 106 outputsthe PHICH signal to PHICH signal receiving section 109.

Broadcast information receiving section 107 reads the content of BCH'splaced in each of a plurality of downlink component bands, received asinput from demultiplexing section 106, and obtains information of theuplink component band associated with each downlink component band.

Then, broadcast information receiving section 107 specifies a downlinkcomponent band in which a BCH to broadcast information related to anuplink component band set for the subject terminal, among the pluralityof downlink component bands, and defines this downlink component band asa downlink semi-reference component band for that terminal.

Also, broadcast information receiving section 107 associates the RBnumber of a PUSCH and the PHICH resource number of a PHICH, and obtainsPHICH resource information indicating the number of PHICH resources.Then, broadcast information receiving section 107 outputs downlinksemi-reference component band information indicating the downlinksemi-reference component band and the PHICH resource information toresource control section 108.

Resource control section 108 specifies a PHICH to which a responsesignal for uplink data from the subject terminal is assigned, based onthe downlink semi-reference component band information and PHICHresource information received as input from broadcast informationreceiving section 107 and uplink resource allocation informationreceived as input from PDCCH receiving section 110. Here, the PHICH towhich the response signal for the uplink data from terminal 100 isplaced in the downlink semi-reference component band for terminal 100among the plurality of downlink component bands. Therefore, resourcecontrol section 108 specifies the downlink component band in which thePHICH is placed, based on the PHICH resource information and downlinksemi-reference component band information. Further, based on the uplinkresource allocation information, resource control section 108 specifiesthe PHICH resource number of the PHICH associated with the RB number ofa PUSCH used to transmit uplink data of the subject terminal. Then,resource control section 108 outputs resource control informationindicating the specified downlink component band and PHICH resourcenumber of the PHICH, to demultiplexing section 106.

On the other hand, control section 201 of base station 200 (FIG. 4)assigns a response signal for the uplink data from each terminal, to aPHICH placed in the downlink semi-reference component band of eachterminal, among a plurality of downlink component bands. That is,regardless of in which downlink component band the uplink resourceallocation information assigned for a terminal having transmitted uplinkdata is placed, control section 201 assigns a response signal for theuplink data from each terminal, to a PHICH placed in the downlinksemi-reference component band of each terminal.

Next, operations of terminal 100 and base station 200 will be explainedin detail.

In the following explanation, as shown in FIG. 11, a PDCCH, PHICH andSCH/BCH are placed in each of two downlink component bands.

Also, terminal 1 and terminal 2 (LTE+ terminals) shown in FIG. 11 eachhave the same configuration as that of terminal 100 shown in FIG. 3.

Also, base station 200 determines which downlink component band anduplink component band are set in every terminal. Here, as shown in FIG.11, the number of downlink component bands set in each terminal is two,and the number of uplink bands is one, which is smaller than the numberof downlink component bands by one. Therefore, as shown in FIG. 11, basestation 200 sets two downlink component bands and one uplink componentband on the lower frequency side (associated with solid lines shown inFIG. 11) to terminal 1, and sets the same downlink component bands asthose of terminal 1 and one uplink component band (associated withdotted lines shown in FIG. 11) to terminal 2. That is, although basestation 200 can use two downlink component bands and two uplinkcomponent bands, each terminal can use only two downlink component bandsand one uplink component band.

Also, although base station 200 reports set downlink component bands anduplink component band to each terminal, in the set component bands, adownlink signal is not necessarily transmitted to each terminal in allsubframes, and transmission of an uplink signal is not necessarilycommanded to each terminal. That is, the downlink component bands setfor each terminal show in which component band a downlink control signaland downlink data for the terminal can be mapped, and the uplink bandset for each terminal shows which uplink component band has to be usedin a case where a terminal receives an uplink control signal.

As shown in the upper part of FIG. 11, each LTE+ terminal (terminal 1and terminal 2) uses PDCCH's placed in two downlink component bands. Incontrast, each LTE+ terminal (terminal 1 and terminal 2) uses only aPHICH placed in the downlink semi-reference component band for eachterminal among the two downlink component bands. Here, thesemi-reference component band for terminal 1 is the downlink componentband on the lower frequency band shown in FIG. 11, in which a BCH tobroadcast information related to an uplink component band used byterminal 1 (i.e., uplink component band on the lower frequency sideshown in FIG. 11) is placed. Also, the downlink semi-reference componentband for terminal 2 is the downlink component band on the higherfrequency side shown in FIG. 11, in which a BCH to broadcast informationrelated to an uplink component band used by terminal 2 (i.e., uplinkcomponent band on the higher frequency side shown in FIG. 11) is placed.That is, terminal 1 and terminal 2 (LTE+ terminals) shown in FIG. 11each specify a downlink component band in which a BCH for LTE tobroadcast information related to an uplink component band set for thesubject terminal is placed, among BCH's for LTE placed in the pluralityof downlink component bands, and determines the specified downlinkcomponent band as a downlink semi-reference component band for thesubject terminal.

A case will be explained below where base station 200 (LTE+ basestation) and terminal 100 (LTE+ terminal) perform communication.

First, control section 201 of base station 200 assigns uplink resourceallocation information and downlink resource allocation information tobe reported to terminal 100, to one of PDCCH's placed in two downlinkcomponent bands shown in the upper part of FIG. 11.

Demultiplexing section 106 of terminal 100 demultiplexes PDCCH signalsplaced in the two downlink component bands shown in the upper part ofFIG. 11, from a reception signal, and PDCCH receiving section 110obtains resource allocation information (uplink resource allocationinformation and downlink resource allocation information) for thesubject terminal, from the demultiplexed PDCCH signals.

Then, mapping section 115 of terminal 100 maps transmission data (uplinkdata) on PUSCH's placed in the uplink component bands shown in the lowerpart of FIG. 11, according to the obtained uplink resource allocationinformation. Here, which uplink component band is set is reported inadvance from base station 200 to terminal 100.

Next, response signal generating section 204 of base station 200generates a response signal (ACK signal or NACK signal) for uplink datafrom terminal 100. Also, control section 201 of base station 200 assignsthe response signal for the uplink data from terminal 100, to a PHICHplaced in a downlink semi-reference component band for terminal 100.Further, control section 201 specifies a PHICH of the PHICH resourcenumber associated with the RB number of a PUSCH assigned to the uplinkdata, among PHICH's placed in the downlink band which is the downlinksemi-reference component band for terminal 100.

That is, as shown in FIG. 11, regardless of in which of PDCCH's placedin two downlink component bands the uplink resource allocationinformation for terminal 100 is placed, control section 201 of basestation 200 performs assignment in a PHICH placed in the downlinkcomponent band which is the downlink semi-reference component band foreach terminal. For example, as shown with solid arrows in FIG. 11, evenin a case where base station 200 transmits uplink resource allocationinformation to terminal 1 (LTE+ terminal) using a PDCCH placed in thedownlink component band on the higher frequency side, control section201 assigns a response signal for uplink data transmitted based on theresource allocation information, to a PHICH placed in the downlinkcomponent band on the lower frequency side (i.e., downlinksemi-reference component band for terminal 1). Also, as shown in dottedlines in FIG. 11, the same applies to terminal 2.

Also, resource control section 108 of terminal 100 selects a downlinksemi-reference component band for that terminal, as a downlink componentband to which a response signal for uplink data is assigned. Forexample, as shown in FIG. 11, regardless of in which of two downlinkcomponent bands a PDCCH assigned resource allocation information forterminal 1 is placed, in the same way as in control section 201 of basestation 200, resource control section 108 of terminal 1 controls aresponse signal for uplink data to be extracted from a PHICH placed inthe downlink component band on the lower frequency side (i.e., adownlink semi-reference component band for terminal 1). Further,resource control section 108 calculates the PHICH resource number of thePHICH associated with the RB number of a PUSCH on which uplink data ismapped. Then, demultiplexing section 106 extracts the response signalfor the uplink data from the PHICH, which is placed in the downlinkcomponent band selected in resource control section 108 and which hasthe PHICH resource number calculated in resource control section 108.

In this way, in a case where asymmetric carrier aggregation is formedfor each LTE+ terminal between uplink and downlink, a downlinksemi-reference component band in which a PHICH assigned a responsesignal for uplink data from an LTE+ terminal is placed, is determinedbased on a BCH for the LTE terminal. By this means, in a case wheredifferent uplink component bands are assigned between LTE+ terminals,each LTE+ terminal can use PHICH resources placed in different downlinkcomponent bands (downlink semi-reference component bands) associatedwith respective uplink component bands. Therefore, even in a system(e.g., LTE+ system) in which the number of uplink component bands andthe number of downlink component bands set for LTE+ terminals isasymmetric, it is possible to avoid the contention for PHICH resourcesbetween LTE+ terminals, so that it is possible to prevent thedegradation in the system efficiency.

Also, a PDCCH to which resource allocation information for a certainterminal is placed in both two downlink component bands. Therefore, evenif PHICH resources placed in one downlink component band are notsufficient, base station 200 can use a PDCCH placed in the otherdownlink component band, so that it is possible to operate PDCCH'sefficiently.

Thus, according to the present embodiment, an LTE+ base station assignsuplink resource allocation information and downlink resource allocationinformation to PDCCH's placed in a plurality of downlink componentbands, and assigns a response signal for uplink data to a PHICH placedin the downlink semi-reference component band for each terminal amongthe plurality of downlink component bands. By this means, even in a casewhere the LTE+ base station uses an uplink component band and downlinkcomponent band with the symmetry unique to each LTE+ terminal (e.g., ina case of using different uplink component bands between LTE+terminals), it is possible to prevent the contention for PHICH resourcesbetween different LTE+ terminals and use the PHICH resourcesefficiently. Therefore, according to the present embodiment, even in acase where asymmetric carrier aggregation is independently formed foreach terminal between uplink and downlink, it is possible to improve theefficiency of frequency use.

Embodiment 6

The present embodiment differs from Embodiment 5 in formingdiscontinuous reception (DRX) independently for each component band, toreduce the power consumption of a terminal.

Although each terminal continuously receives a setting report of twodownlink component bands from a base station, it is rare in fact thatthere are many consecutive signals to be transmitted in the time domainfrom the base station to each terminal, so that it is sufficient for theterminal to receive only one downlink component band in one time.Therefore, it is possible to reduce the power consumption in a terminalby determining in advance DRX operations between a base station andterminal in a certain component band, where the DRX operations representoperations in which the terminal receives a signal in the component bandin partial time (period) and does not receive a signal in the componentband in other time (period) than the partial time. Here, focusing on onecomponent band, a cycle formed with “a period of receiving a signal” and“a period of stopping receiving a signal,” is called “DRX cycle.” TheDRX cycle is repeated in, for example, several tens of ms cycles.

In this case, the terminal performs DRX independently for every downlinkcomponent band. Here, for example, in FIG. 11 (Embodiment 5), even in acase where uplink resource allocation information for terminal 1 istransmitted using a PDCCH placed in the downlink component band on thehigher frequency side, the base station has to transmit a responsesignal using a PHICH placed in the downlink component band on the lowerfrequency side (i.e., semi-reference component band for terminal 1).However, depending on the DRX cycle, a case is possible where, even ifthe terminal can receive a signal in the downlink component band on thehigher frequency side, the terminal cannot receive a response signalbecause the downlink component band on the lower frequency side is in astate of DRX (i.e., while stopping reception).

Therefore, with the present embodiment, as shown in FIG. 12, theimportance level is assigned to downlink component bands in which aPHICH assigned a response signal for each terminal is placed.

This will be explained below in detail. Similar to Embodiment 5, eachterminal according to the present embodiment specifies a downlinkcomponent band in which a PHICH assigned a response signal for thesubject terminal is placed, based on information of a semi-referencecomponent band for that terminal. Here, if the semi-reference componentband is in a state of DRX at the reception timing of a response signal,the terminal determines a downlink component band in which a PDCCH usedto transmit uplink resource allocation information is placed, as adownlink component band in which a PHICH used to receive the responsesignal is placed.

For example, as shown in FIG. 12, in a case where uplink resourceallocation information is transmitted using a PDCCH placed in thedownlink component band on the higher frequency side, normally, terminal1 extracts a response signal for uplink data from a PHICH placed in thedownlink component band on the lower frequency side, which is a downlinksemi-reference component band for the subject terminal, in the same wayas in Embodiment 5. However, in a case where the component band on thelower frequency side shown in FIG. 12 is in a state of DRX, terminal 1extracts a response signal for uplink data from a PHICH placed in thesame downlink component band on the higher frequency side as that of aPDCCH used to transmit uplink resource allocation information for thatterminal. Here, similar to Embodiment 5, the PHICH resource number isdetermined in association with the RB number of the PUSCH used totransmit the uplink data.

That is, in FIG. 12, terminal 1 gives an importance level of the firstplace to a PHICH placed in the downlink component band on the lowerfrequency side (i.e., downlink semi-reference component band forterminal 1), and gives an importance level of a second place to a PHICHplaced in the downlink component band on the higher frequency side.Then, terminal 1 specifies a PHICH to which a response signal for uplinkdata from that terminal is assigned, according to the importance levelof the PHICH and the state of DRX. In FIG. 12, terminal 2 also sets theimportance levels of PHICH's in the same way (not shown).

Thus, according to the present embodiment, a terminal gives animportance level to PHICH's placed in a plurality of downlink componentbands assigned to that terminal as downlink component bands in whichPHICH's to receive a response signal are placed. Basically, the terminalreceives uplink resource allocation information using a PDCCH placed ina downlink component band that is not in a state of DRX, and,consequently, upon receiving a response signal for uplink data, there isa high possibility that a downlink component band in which the PDCCH isplaced is not in a state of DRX. Therefore, according to the presentembodiment, in a case where DRX is performed independently everycomponent band, it is possible to reduce the overhead of PHICH resourcesand prevent a terminal from not being able to receive a PHICH to which aresponse signal for that terminal is assigned.

Also, a case has been described above with the present embodiment where,upon receiving a response signal using a PHICH resource (e.g., PHICH ofan importance level of “2” shown in FIG. 12) placed in the same downlinkcomponent band as that of a PDCCH used to receive uplink resourceallocation information, a terminal extracts the response signal from thePHICH of the PHICH resource number associated with the RB number of thePUSCH. However, according to the present invention, a PHICH from which aterminal extracts a response signal is not limited to a PHICH associatedwith the RN number of a PUSCH, and it is equally possible to use a PHICHseparately reported to the terminal. There is a very low possibilitythat a PHICH of a lower importance level (PHICH with an importance levelof “2” in FIG. 12) is used. Therefore, if a base station reports a PHICHresource with a lower importance level to a terminal, this PHICHresource is shared with other terminals by easy scheduling control onthe base station side, so that the overhead of this PHICH resourcebecomes extremely small.

Embodiments of the present invention have been described above.

Also, Embodiments 1 to 4 of the present invention may be applied only toa case where the communication bandwidths are asymmetric between uplinkand downlink, that is, where the number of uplink component bands issmaller than the number of downlink component bands.

For example, in a case where the communication bandwidths are symmetricbetween uplink and downlink (where the ratio of communication bandwidthsis 1:1 between uplink and downlink), as shown in FIG. 13, a terminalselects a PHICH placed in the same downlink component band as a downlinkcomponent band in which a received PDCCH is placed. In contrast, in acase where communication bandwidths are asymmetric between uplink anddownlink, similar to the above embodiments (e.g., FIG. 5 and FIG. 6), aterminal selects a PHICH placed in a partial downlink component band(the LTE/LTE+ coexisting band). However, although a case has beendescribed with FIG. 13 where the partial component band is the LTE+band, the present invention is equally applicable to a case where allcomponent bands are LTE/LTE+ coexisting bands in FIG. 13.

Also, although channel allocation of a downlink response signal foruplink data have been described with Embodiments 1, 2, 5 and 6 of thepresent invention, the present invention is equally applicable tochannel allocation of an uplink response signal for downlink data. Forexample, in a case where one downlink component band is associated witha plurality of uplink component bands, a terminal assigns an uplinkresponse signal to uplink response signal resources placed in a samenumber of partial uplink component bands (e.g., LTE/LTE+ coexistingband) as the number of downlink component bands among the plurality ofuplink component bands. That is, regardless of in which uplink componentbands a PDCCH or PDSCH placed in one downlink component band isreceived, the terminal assigns a response signal for uplink responsesignal resources placed in the partial uplink component band. Even inthis case, it is possible to provide the same effect as in the aboveembodiments.

Also, although cases have been described above with embodiments where anSCH/BCH is not placed in an LTE+ band, with the present invention, anSCH/BCH that can be received by an LTE+ terminal may be placed in theLTE+ band. That is, with the present invention, regardless of whether ornot an SCH/BCH is present, a component band in which an LTE terminal isnot contained is referred to as “LTE+ band.”

Also, with the above embodiment, for ease of explanation, a PHICH andPDCCH are time-divided for the placement of PHICH and PDCCH (e.g., FIG.5 and FIG. 6). That is, resources that are orthogonal in the time domainare allocated to a PHICH and PDCCH, respectively.

However, with the present invention, placement of PHICH and PDCCH is notlimited to this. That is, resources having respective frequencies, timesor codes, that is, orthogonal resources are assigned to a PHICH andPDCCH, respectively.

Also, although cases have been described above with embodiments wherethe communication bandwidth of a component band is 20 MHz, thecommunication bandwidth of a component band is not limited to 20 MHz.

Although example cases have been described above with Embodiments 1 to 4where the present invention is implemented with hardware, the presentinvention can be implemented with software.

Furthermore, each function block employed in the description of each ofEmbodiments 1 to 4 may typically be implemented as an LSI constituted byan integrated circuit. These may be individual chips or partially ortotally contained on a single chip. “LSI” is adopted here but this mayalso be referred to as “IC,” “system LSI,” “super LSI,” or “ultra LSI”depending on differing extents of integration.

Further, the method of circuit integration is not limited to LSI's, andimplementation using dedicated circuitry or general purpose processorsis also possible. After LSI manufacture, utilization of an FPGA (FieldProgrammable Gate Array) or a reconfigurable processor where connectionsand settings of circuit cells in an LSI can be regenerated is alsopossible.

Further, if integrated circuit technology comes out to replace LSI's asa result of the advancement of semiconductor technology or a derivativeother technology, it is naturally also possible to carry out functionblock integration using this technology. Application of biotechnology isalso possible.

The disclosures of Japanese Patent Application No. 2008-205644, filed onAug. 8, 2008, Japanese Patent Application No. 2008-281390, filed on Oct.31, 2008, Japanese Patent Application No. 2008-330641, filed on Dec. 25,2008, including the specifications, drawings and abstracts, areincorporated herein by reference in their entireties.

INDUSTRIAL APPLICABILITY

The present invention is applicable to a mobile communication system,for example.

The invention claimed is:
 1. A communication apparatus comprising: areceiver, which, in operation, receives downlink resource allocationinformation for each of a plurality of downlink component carriers;receives downlink data on each of the plurality of downlink componentcarriers; receives uplink resource allocation information transmitted onone downlink component carrier out of the plurality of downlinkcomponent carriers on which the receiver receives downlink data; and atransmitter, which, in operation, transmits uplink data on an uplinkcomponent carrier in accordance with the uplink resource allocationinformation, wherein the receiver, in operation, receives anAcknowledgement/Negative-acknowledgement (ACK/NACK) signal for theuplink data only on said one downlink component carrier on which theuplink resource allocation information is transmitted out of theplurality of downlink component carriers.
 2. The communication apparatusaccording to claim 1, wherein the ACK/NACK signal for the uplink data isreceived in a first channel on said one downlink component carrier, thefirst channel being different from a second channel, in which downlinkresource allocation information is received.
 3. The communicationapparatus according to claim 2, wherein the first channel is a physicalhybrid-ARQ indicator channel (PHICH), and the second channel is aphysical downlink control channel (PDCCH).
 4. The communicationapparatus according to claim 1, wherein a number of uplink componentcarriers is equal to or less than a number of the plurality of downlinkcomponent carriers.
 5. A communication method comprising: receivingdownlink resource allocation information for each of a plurality ofdownlink component carriers; receiving downlink data on each of theplurality of downlink component carriers; receiving uplink resourceallocation information transmitted on one downlink component carrier outof the plurality of downlink component carriers on which downlink datais received; transmitting uplink data on an uplink component carrier inaccordance with the uplink resource allocation information; andreceiving an Acknowledgement/Negative-acknowledgement (ACK/NACK) signalfor the uplink data only on said one downlink component carrier on whichthe uplink resource allocation information is transmitted out of theplurality of downlink component carriers.
 6. The communication methodaccording to claim 5, wherein the ACK/NACK signal for the uplink data isreceived in a first channel on said one downlink component carrier, thefirst channel being different from a second channel, in which downlinkresource allocation information is received.
 7. The communication methodaccording to claim 6, wherein the first channel is a physical hybrid-ARQindicator channel (PHICH), and the second channel is a physical downlinkcontrol channel (PDCCH).
 8. The communication method according to claim5, wherein a number of uplink component carriers is equal to or lessthan a number of the plurality of downlink component carriers.